Picknell was born in Springfield, Vermont in 1864, and studied in Paris with Constant and Lefebvre (1887-1890). After his studies in Paris, he was briefly an illustrator in Boston and New York. He returned to Paris for about fifteen years, painting throughout the country. He returned to the U.S. around 1911, and was active in Freehold, NJ before settling in Silvermine, CT, in 1912 where he founded the Silvermine Artists Guild. During WWI, he and his wife opened the Fine Arts Theatre in Westport, CT. He is best known for his landscapes of Connecticut and rural France.

Picknell was also a founding member of the American Artists’ Association of Paris, as well as a member of the Salmagundi Club. He exhibited extensively in both France and the United States. His brother was the artist William Lamb Picknell.